I'm just throwing this idea out there. I should note I've not missed this feature for the last 15 or so years I've been using SpamGourmet.
Could the server keep track of the last time
a) a message was forwarded
b) a message was eaten (If no messages have been eaten it could display in green, "All messages forwarded."
This could go on the 'my emails screen'
The columns could be:
[I would put created (UTC) here]
[ New: ] forward date
[ New: ] delete date
[ I'd move left:] created (UTC)
Again, I should note that I would not put a lot of money into this.